Traditional dumbbells and barbells have been used for over a century for building body strength and continue to be used for general fitness, strength and endurance training, and physical rehabilitation.
There are two types of dumbbells: fixed and adjustable.
Fixed dumbbells are typically one solid piece of metal with a handle in the center. Fixed dumbbells present a problem for storage in limited space, being that usually two of each weight increment takes up a significant amount of room. Each set must also be purchased separately, making an entire set rather expensive. A set of fixed dumbbells is also not very portable, specifically moving the entire set is very inconvenient.
There are a variety of adjustable dumbbells designs, ranging from simple to very elaborate. Each of the existing designs has significant drawbacks. They stricken with one or more of the following problems: they take too much time to change weight, are not useable by someone with large hands, are unwieldy, are difficult to change weights, or pose a safety hazard.
The initial designs for adjustable dumbbells included individual disc-shaped weights with holes in the center that would slide onto a round bar and secured to the handle by means of some sort of locking collar. These collars might screw on, use a spring clamp, or have a collar with a threaded locking pin. If the collars are loose or loosen during use, they pose a safety hazard because the weights can fall off the handle.
Some innovative designs of adjustable dumbbells have appeared in the last decade. They use either an internal or external mechanism that attaches a desired number of weights to a handle. Although these designs show some promise, each has drawbacks and limitations.
These limitations include such elements as: external selection mechanisms which pose a safety hazard, mechanisms that are limited in their function, mechanisms that are overly complicated, mechanisms that prohibit general usefulness or user comfort, devices that would not be reliable or sturdy, or some combination of the above. Some concepts that the present devices uses are mentioned in previously submitted material, but are not put together to make a safe, versatile, durable and user-friendly mechanism. There is room among these innovations for further advancement in design and application.
The rack-and-pinion system is not a new technology. The present invention is unique in using not only the rack-and-pinion system, but combining it with a basic gear drive to extend the travel of the sliding elements, increasing the number of weights that the device may hold. This transmission system is also unique in that it further adds both safety and convenience of not having a users hand on the weight selection device during normal use.
The present invention utilizes specific design features that ensure proper function. Unlike previous devices, the present devices contains all of the following features: a rack-and-pinion device contained within the handle, a basic transmission for maximum travel of extendable elements, mechanisms for locking extendable elements in each incremental position, indicator of currently selected weight, and nested weight units that have bars attached to the sides of the plates for required support.
In summary, the present invention is the next generation of adjustable dumbbells, using both established concepts and new design features to create the simplest and safest adjustable dumbbell.